This invention relates to the separation of bitumen from tarsands and, more particularly, relates to the separation and recovery of bitumen from tarsands such as occur, for example, in the Athabasca tarsands in Alberta, Canada, by flotation at ambient temperatures.
Flotation processes for the beneficiation of bitumen from tarsands at temperatures of about 85.degree. C, known as hot water flotation processes and typified by the Clark hot water process, are well known. However, such processes require the input of considerable thermal energy, much of which is not recoverable and is lost in the discharge of tailings which constitute in excess of 80% of the materials handled in the form of water and spent sands. Conventional hot water process plants must also normally be located in proximity to a supply of heat, thus necessitating costly transportation of the tarsands to central processing units close to thermal plants such as oil refineries.
The separation of bitumen from tarsands at substantially ambient temperatures would obviate the need for the separation plant to be close to a supply of heat and would permit separation of bitumen from the sands in proximity to the mining operation, thus minimizing the cost of transporting the solids which comprise by far the bulk of the materials handled, while facilitating the return of separated sand and fine solids to disposal areas.
Conventional dry mining of tarsands is accomplished by means of power shovels, draglines, bucketwheels and the like large earth moving equipment. Wet mining can be accomplished in open pits by means of rotary excavators in combination with slurry pumps operating from a dredge or by waterjets in combination with mechanical equipment, and for deep deposits, by means of high pressure water jets in combination with slurry pumps in boreholes. A flotation process which operates at ambient temperatures would provide the important advantage of permitting the choice of conventional dry mining techniques or wet mining techniques, the dry mining techniques employing hydraulic pipeline transportation of the mined tarsands to a separation plant and the wet mining techniques employing dredge mining, waterjetting or borehole mining with the option of hydraulic pipeline transportation of the tarsands to a separation plant or the processing of the tarsands on a dredge or adjacent a plurality of boreholes in an integrated mining and beneficiation operation with return of tailings directly to a tailings pond.
Dredge mining, waterjet mining in open pits or borehole mining of tarsands integrated with an ambient or low temperature flotation process would provide the important advantage of utilizing the shear energy consumed during the mining operation in water for initial disintegration of the tarsands and fragmentation of the bitumen for release from the sands preliminary to flotation.
Canadian Pat. No. 741,301 discloses the use of mechanical agitation and high energy water jets to form a slurry for flotation of bitumen in a hot water process. Canadian Pat. No. 915,608 discloses the use of shearing energy applied to an aqueous bituminous emulsion to coalesce and remove water therefrom at medium temperatures. The separation and recovery of bitumen from tarsands at ambient temperatures, i.e. "low temperatures" below about 35.degree. C., has heretofore not been considered feasible or commercially viable.